This invention relates to sense amplifiers for memories, and more particularly, to sense amplifiers for magneto-resistive random access memories (MRAMs).
MRAM technology has become an attractive memory for non-volatile applications because of its high density and relatively high speed. One of the difficulties with MRAMs, however, is the relatively small difference between the high and low logic states of the magnetic tunnel junction (MTJ). The two states are distinguished by a resistance difference of about 40% at zero volts bias on the MTJ. Detecting the state of the bit requires a non-zero bias and the rate at which the signal being detected develops typically increases as the bias across the MTJ increases. As the bias across the MTJ increases, however, the resistance difference between the high and low states decreases. For example, increasing the bias across the MTJ to 300 milli Volts (mV) decreases the resistance difference to only 25%. Thus, there is a conflict between the rate of the development of the signal and the magnitude of the signal differential.
Accordingly, there is a need for a sense amplifier that at least reduces the adverse effects of this conflict.